Studies have continued toward the development of a guinea pig model to study Epstein Barr Virus (EBV), a virus implicated in human cancer, and Herpes saimiri (HVS), a virus known to transform human cells in vitro. Chronically infected pigs have consistently exhibited serum antibodies to EBV and HVS as judged by immunofluorescence. Tumor promoting agents, such as procarbazine and TPA, have been injected into these animals to promote the carcinogenic activity of these viruses.